In recent years, in view of energy saving and environmental conservation, illumination apparatuses (such as light-emitting diode lamps) using a light-emitting diode (hereinafter also referred to as “LED”) as a light source have been increasingly used in place of incandescent lamps or fluorescent lamps. Conventional illumination apparatuses using LEDs as the light source, however, emit light only in the forward direction (the emission direction of light from the light source), and cannot emit light in a wide range unlike incandescent lamps or fluorescent lamps. Therefore, unlike incandescent lamps or fluorescent lamps, the conventional illumination apparatuses cannot illuminate a wide range of a room by utilizing the reflection light of the ceiling and walls.
To make the light distribution characteristics of the conventional illumination apparatuses using LEDs as the light source close to the light distribution characteristics of incandescent lamps or fluorescent lamps, it has been proposed to control the light distribution of light emitted from LEDs by a light flux controlling member (see, for example, PTLS 1 and 2). FIG. 1A to FIG. 1C illustrate a configuration of the light flux controlling member disclosed in PTLS 1 and 2. FIG. 1A is a perspective view of light flux controlling member 10 disclosed in PTL 1, and FIG. 1B illustrates light paths in light flux controlling member 10 disclosed in PTL 1. In addition, FIG. 1C illustrates light paths in light flux controlling member 50 disclosed in PTL 2.
As illustrated in FIG. 1A and FIG. 1B, light flux controlling member 10 disclosed in PTL 1 includes bottom surface 20, first side surface 30, and second side surface 40. Bottom surface 20 includes support surface 21 and incidence surface 22. In addition, incidence surface 22 includes first incidence surface 23, second incidence surface 24, and third incidence surface 25. First side surface 30 includes first projecting surface 31 and first reflecting surface 32. Second side surface 40 includes second projecting surface 41 and second reflecting surface 42. In light flux controlling member 10 disclosed in PTL 1, a part of light emitted from the light source is incident on first incidence surface 23 and emitted from first projecting surface 31. In addition, another part of the light emitted from the light source is incident on second incidence surface 24 and reflected by first reflecting surface 32, and, emitted from second projecting surface 41. Further, another part of the light emitted from the light source light is incident on third incidence surface 25 and then reflected by second reflecting surface 42 and first reflecting surface 32, and, emitted from second projecting surface 41.
As illustrated in FIG. 1C, light flux controlling member 50 disclosed in PTL 2 includes incidence surface 60, projecting surface 70, and total internal reflection surface 80. Incidence surface 60 includes first incidence surface 61 and second incidence surface 62. Projecting surface 70 includes first projecting surface 71 and second projecting surface 72. In light flux controlling member 50 disclosed in PTL 2, a part of light emitted from the light source is incident on first incidence surface 61 and emitted from first projecting surface 71. In addition, another part of the light emitted from the light source is incident on light second incidence surface 62, and then internally reflected by total internal reflection surface 80, and, emitted from second projecting surface 72.
By controlling the travelling direction of the light emitted from the light source with use of light flux controlling members 10 and 50, it is possible to obtain emission light not only in the forward direction but also in the lateral direction.